Add if statement back into publishing workflow

Author: alexgdebeer

.github/workflows/publish_pypi.yaml

@@ -34,6 +34,7 @@ jobs:
   publish-to-pypi:
     name: >-
       Publish Python distribution to PyPI
+    if: startsWith(github.ref, 'refs/tags/')  # only publish to PyPI on tag pushes
     needs:
     - build
     runs-on: ubuntu-latest